This program is designed to examine in detail several biological, biochemical and immunological aspects of peptide hormones which influence mineral metabolism. The two principal peptides are the calcium-mobilizing hormone of the parathyroid gland (parathyroid hormone) and the thyroid hypocalcemic peptide (thyrocalcitonin). The relationship of structure to biological and immunological activities of parathyroid hormone and thyrocalcitonin will be examined. The other goals include the development of assay methods capable of detecting physiological concentrations of these peptides in plasma and in tissues, purification and characterization of polypeptide chains, and investigations of the mechanisms which control the secretion of these hormones and by which they exert their physiological effects.